Fast switching between digital video sources

ABSTRACT

A sink may be to used to process multimedia digital data. The sink may include a plurality of input ports, an output port, a switchably-enabled selector to select an input port from a plurality of HDMI input ports to couple to an output port, a control circuit to detect encrypted data in a channel of the input ports; and a plurality of decryption engines. Each of the decryption engines may be coupled to respective input ports to synchronize with a corresponding encryption engine of a data source after the control circuit detects encrypted data in the channel of the respective input port. Additional circuitry may be included to operate the sink in a power saving mode. Also, methods for processing the data in both power saving and non-power saving modes.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/287,562, filed Dec. 17, 2009, which is incorporatedherein by reference in its entirety.

BACKGROUND INFORMATION

High definition multimedia interfaces (HDMI) have been used to digitallytransmit audio and video between different multimedia sources, such asDVD players, gaming consoles, and cable television set top boxes, todifferent display devices, such as televisions or video projectors. HDMIaudio and video signals may be transmitted over three separate serialdigital data streams on three channels. Each of these three data streamsmay include active video data frames, such as pixel data and the like.

Audio and video signal transmitted over HDMI may be received at a HDMIsink. An HDMI sink may include multiple input ports for receiving HDMIaudio and video data from multiple sources. An HDMI television, forexample, may have a HDMI sink with three or more HDMI input ports forreceiving signals from different input sources, such as DVD players,cable television set top boxes, and video game consoles. A user can thenselect the HDMI input source that they want to watch on the television.

To prevent unauthorized copying of audio and video programs, some of thedata on these channels may be encrypted. The data that may be encryptedcould include some or all of the video and/or audio data on at least oneof the three channels. The HDMI sink can decrypt encrypted data using adecryption engine and then convert it to a format compatible with thetelevision set, for example, so the video can be seen and the audio canbe heard.

Existing HDMI sinks tend to consume a relatively large amount of power.In order to conserve power, some existing HDMI sinks power down theinput ports of non-selected input ports, leaving only one input portpowered up. The input port left powered up may be the selected inputport of a source currently being viewed on the television, for example.One of the problems with powering down non-selected input ports is thatwhen a user wants to switch inputs, say from a DVD player to a cable settop box, the user may have to wait up to ten seconds or more for thedecryption engine of the powered up port to authenticate and synchronizewith the encryption engine of the newly selected input source.

Instead of powering down all channels in non-selected input ports, anattempt may be made to only power down a subset of data channels in eachinput port. However, when these powered down channels are subsequentlypowered up, invalid data may be produced due to timing mismatchesbetween channels leading to a loss of authentication. The timingmismatches may occur because the circuits in HDMI sinks may include anumber of serially disposed data processing elements to perform specificfunctions on the digital data in order to generate the actual video andaudio outputted to the user. For example, one data processing elementmay perform a filtering function, while another performs a decodingfunction and a third performs an interleaving process. However, the timerequired by each of these elements to perform their respective functionsmay vary. For example, one of the data processing elements may requireonly one or two clock cycles to perform its function, while another maytake five or more clock cycles to carry out its function on the data.

Since the digital data elements are arranged in series, the initial dataproduced by some of the data processing elements after being initiallypowered up may be invalid data. This invalid data may result fromresidual data left in the processing element from a previous power upcycle and may cause additional delays in producing data suitable fordisplay on a video device. The invalid data may cause undesirabledistorted images to be initially displayed on the digital video displaydevice.

There is a need to minimize power consumption in HDMI sinks whileenabling fast switching between input sources containing encrypted data.There is also a need to eliminate invalid data produced by some serialdata processing elements when initially powering up the elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description of an embodiment of the invention is given byway of example only with reference to the accompanying drawings.

FIG. 1 is a block schematic representation of a HDMI sink in anembodiment of the invention.

FIG. 2 is a block representation of a digital signal processor and aninput port of the HDMI sink of FIG. 1.

FIG. 3 is a block representation of a existing digital data processingsystem for use in a sink.

FIG. 4 is a block representation of a digital data processing system inan embodiment of the invention.

FIG. 5 shows a block representation of a different embodiment of theinvention.

FIG. 6 shows another block representation of a different embodiment ofthe invention.

DETAILED DESCRIPTION

An embodiment of the invention may include a sink with multiple inputports for receiving digital audio/video data from different sources. Thesink may also include an output port. Audio/video data from a selectedinput port source may be processed and outputted to a digital signalprocessing device, such as a television, digital video recorder, orother device. The sink, sources, and data may be HDMI compliant. Each ofthe input ports may include multiple channels for receiving respectiveserial digital data streams and a display data channel. The non-selectedinput ports coupled to sources transmitting encrypted data may keep theprocessing elements and components of at least one data channel poweredup to maintain continuous authentication with respective sources, evenwhen switching between the power savings and non-power savings modes. Acontrol circuit may send a signal to a channel of non-selected inputports to power down data processing elements and components of thatchannel when operating in a power savings mode. The powered downelements and components may then be powered up when switching to anon-power savings mode.

The remaining channels of each input port may stay powered up in both apower saving mode and a non-power saving mode. In a three channel port,for example, the first channel may carry vertical sync signals and thirdchannel may carry encryption enable signals. Both of these channels maystay powered up in both the power saving and non-power saving modes,while the elements and components in the second channel may then bepowered down and powered up when switching between the power saving andnon-power saving modes. A control circuit may send power up and powerdown signals to the input ports to power up and power down at least someof the elements and components in the second channel of ports exiting orentering the power saving mode.

The control circuit may monitor the first and third channels in eachnon-selected input port to detect encrypted data frames and maintainauthentication and synchronization with the encryption engines ofrespective non-selected sources. The control circuit may detectencrypted data by detecting vertical sync signals in the first channeland at least a part of the corresponding encryption enable code in thethird channel indicating when a subsequent data frame is encrypted.

The sink may include a decryption engine associated with each inputport, a key storing means, such as a memory, to store decryption keys todecrypt data in the serial data streams, a digital signal processingcircuit to produce decryption codes for respective decryption engines,and a control circuit to control access to decryption keys to make themsequentially accessible for authentication functions.

Other embodiments may have different sink configurations. Some HDMIcircuit configurations may include multiple sinks, each with its ownsink input port, decryption engine, and output port. Each of the sinksmay be implemented as integrated circuits that are part of the HDMIcircuit, which may be implemented as a single integrated circuitincluding at least one HDMI interface. Audio/video data from a HDMIsource connected to a sink input may be processed and outputted at theoutput port of the sink. The output ports of each sink may be connectedto a primary output port of the circuit through a digital data path.

The digital data path may include a multiplexer. The multiplexer mayselectively connect the output port of different sinks in the circuit tothe primary output port of the circuit. This selective connection mayoccur in response to a source select signal indicating which sink outputport should be selectively connected to the primary output port.

In an embodiment, each of the output ports may be connected to theprimary output port. Each of the output ports may be operated in anormally disabled mode where audio and video signals are prevented frombeing outputted through a sink output port. Each output port may beswitched to an enable mode where audio and video signals processed bythe sink are outputted through the sink output port to the primaryoutput port of the circuit. A source select signal may enable a selectedsink output port and disable an unselected output port.

The control circuit may control access to decryption keys using a queueto process authentication requests in the order they were received fromeach input port. The authentication requests may be transmitted frominput sources requesting authentication over the display data channeland the control circuit may monitor the display data channels of theinput ports for the authentication requests, which may be added to thequeue after detection. Accordingly, the control circuit may samplesignals on the display data channel of the input ports at a higherfrequency than that of data on the display data channel. In someembodiments, the control circuit may sample signals on the display datachannels at a frequency that is at least 10 times greater than thefrequency of data on the channels. For example, in an embodiment whereeach symbol is represented by 10 bits and each bit is oversampled by afactor of 3, the control circuit may sample signals on the display datachannels at a frequency that is 30 times greater than the frequency ofthe data on the channels.

Once the control circuit detects an authentication request at an inputport, the digital signal processing circuit of that input port maypermit writing of a key selection vection (AKSV) at the display datachannel of the input port to a temporary storing means, such as amemory. The digital signal processing circuit may also read decryptionkeys stored in the key storing means after receiving access from thecontrol circuit and compute a decryption code based on the decryptionkeys and the key selection vector AKSV. The decryption code may beupdated in response to receiving a vertical sync signal on the firstchannel and at least a part of an encryption enable signal on the thirdchannel of the input port. The decryption code may still be updated whenoperating in the power saving mode.

In an embodiment, the digital signal processing circuit may also produceits own key selection vector (BKSV) that is transmitted over the displaydata channel of one or more input ports. A source connected to an inputport may then read the key selection vector BKSV and calculate its owncode to facilitate authentication of the decryption engine on therespective port.

The data processing elements in each channel may include a serial toparallel data converter, a delay circuit, and a decoding circuit todecode transmission line encodings into natural binary, which may all becapable of processing parallel data. In some embodiments, the dataprocessing elements may also include a high bandwidth digital contentprotection (HDCP) circuit, which may be adapted to process paralleldata. The serial to parallel converter may convert serial digital datain a channel to parallel data and the delay circuit may delay theparallel data in each channel of an input port until the parallel datain all three channels of the input port are aligned. When an input portin a power savings mode is switched to a non-power savings mode andpowered up, each of the data processing elements in the second channelmay be progressively enabled. The progressive enabling may be triggeredby a data enable signal generated at a preceding data element when thepreceding data element processes valid data.

The components in each channel may include at least one of an automaticgain control circuit, a sampling circuit, and an equalizer circuit. Whenpowering down components in the second channel of an input port in apower savings mode, the sampling circuit in the second channel may bepowered down first, followed by the equalizer circuit, and then theautomatic gain control circuit. The reverse sequence may be used topower up these elements when switching to a non-power savings mode.Delays between powering components in the range of about 0.5 to 5 ms,about 1 to 3 ms, and about 1 ms may be used in different embodiments,though other delays outside these ranges are also possible in otherembodiments.

The control circuit may also be configured to periodically power upelements and/or components in the second channel of ports in the powersaving mode in order to retrieve data from a video signal supplied tothe port. This data may include a horizontal or vertical parameter ofthe video, a type of incoming audio samples, a color depth in bits ofvideo data, a pixel repetition rate, or other information.

FIGS. 1 and 2 show a configuration of a HDMI sink 1 in an embodiment ofthe invention for receiving serial digital video and/or audio datastreams from respective HDMI sources (not shown). An HDMI sink 1 mayinclude four input ports 2 a, 2 b, 2 c and 2 d that may receive HDMIdata streams from the respective HDMI sources. In some embodiments, thedata in at least one of the HDMI data streams may be encrypted. Each ofthe input ports 2 b, 2 c, and 2 d may be similar to the input port 2 a,which is illustrated in detail in FIG. 2. The data streams from therespective HDMI sources (not shown) may originate from any audio andvideo HDMI source, such as a DVD player, a gaming station, a set top boxfrom a cable provider, or any other HDMI source.

The HDMI sink 1 may process and convert the serial digital data streamsreceived at the respective input ports 2 through the digital signalprocessor 4 in order to generate digital video and/or audio signalscompatible with a digital video display device, such as a digitaltelevision set or other digital video signal processing device, whichmay be outputted at an output port 3 of the HDMI sink 1. The digitalsignal processor 4 may be located within a control circuit 5. Thecontrol circuit 5 may control operation of the HDMI sink and the digitalsignal processor 4. FIGS. 3 and 4 show some configurations of digitalsignal processor 4.

Each input port 2 may include three channels, namely, a first channel 6,generally referred to as “channel zero,” a second channel 7, generallyreferred to as “channel one,” and a third channel 8, generally referredto as “channel two.” Each of these three channels 6, 7, and 8 mayreceive respective serial digital data streams. The serial digital datastreams may include active video content, audio and other packet data,and/or control and status signals. The nature of the active videocontent on each of the three channels 6, 7, and 8 depends on the formatof data being transmitted from the HDMI source (not shown) to the HDMIsink 1. If, for example, the video data is being transmitted in the RGBformat, channel 6 may carry pixel color data relating to the color blue,channel 7 may carry pixel color data relating to the color green, andchannel 8 may carry pixel color data relating to the color red.

However, regardless of the data format selected, channel 6 may transmitvertical and horizontal sync codes and channels 7 and 8 may transmitrespective bits of an encryption enable code which may be indicative ofthe encryption status of the next following frame of active video data.In some embodiments, the bit of the encryption enable code transmittedon channel 8 may be in either a high or low state when the next frame ofdata is encrypted, and may be in the opposite state when the next frameof data is not encrypted. Accordingly, by monitoring channel 6 for thecode representative of the vertical sync signals, and channel 8 for therelevant bit of the encryption enable code, the encryption status ofeach frame of data carried on the three channels 6, 7 and 8 can bereadily determined. This principle may be used in an embodiment tominimize power consumption.

The serial data streams on channels 0, 1 and/or 2 may also be monitoredto detect a display enable signal transition from an inactive to anactive state, and also from an active to an inactive state. Transitionsfrom inactive to active states may be used to identify the start ofactive video data in the three data streams and transitions from activeto inactive states may be used to identify the start of blankingregions. Data representing these signal transitions may be extractedfrom one or more of the channels. A blanking region may include verticaland horizontal sync signals, control and other data, digital packetaudio data, and encryption enable code signals.

Each input port 2 may also include other channels. For example, an inputport may include a clock channel 9 that receives a clock signal from thecorresponding HDMI source. The clock channel 9 may include a phase lockloop 10 for recovering and cleaning the clock signal received from thecorresponding HDMI source. A display data channel (DDC) 11 may transferhand shaking data between the HDMI source and the HDMI sink using aprotocol such as I²C, though other embodiments may use differentprotocols. The display data channel may also be used to transferencryption and/or decryption data. Other channels (not shown) may alsobe used to transmit signals of different applications and/or verifyconnectivity between a HDMI source and a corresponding input port 2 ofthe HDMI sink 1.

Differential signaling may be used to transmit data in the serialdigital data streams of each channel 0, 1, and 2. Terminating resistorsRT0, RT1, and RT2 may be used to terminate the differential inputs ofeach respective channel 0, 1, and 2, of an input port 2. A differentialclock signal may be transmitted over the clock channel 9, anddifferential protocol and handshaking signals may be transmitted overthe DDC channel 11. Terminating resistors RT3 and RT4 may also be usedto terminate the differential inputs of the clock channel 9 and DDCchannel 11, respectively.

An automatic gain control circuit 15 may be included in each channel 0,1, and 2, to adjust the gain of the data stream in the correspondingchannel. For convenience, the automatic gain control circuit 15 ofchannel 0 may be identified by the reference numeral 15 a, the automaticgain control circuit 15 of channel 1 may be identified by the referencenumber 15 b, while the automatic gain control circuit 15 of channel 2may be identified by the reference numeral 15 c. Each channel 0, 1 and 2also may include an equalizer circuit 16 to equalize the channel gainwith frequency of the data signals in the data stream. The equalizercircuit 16 of channel 0 is identified by the reference numeral 16 a,while the equalizer circuits 16 of channels 1 and 2 are identified bythe reference numerals 16 b and 16 c, respectively.

Each channel 0, 1 and 2 may also include a sampling circuit 17 to sampledata from the data stream of that channel. The sampled data may be sentto the digital signal processor 4. The sampling circuit 17 of channel 0may be identified by the reference numeral 17 a, while the samplingcircuit 17 of channels 1 and 2 may be identified by the referencenumerals 17 b and 17 c, respectively.

Each input port 2 may have a phase recovery circuit 18 to recover theoptimal phases of oversampled data in each of the sampling circuits 17a, b, and c.

Each input port 2 may also have a decryption engine 20 to decrypt theencrypted data in the serial data streams of each channel 0, 1, and 2.In the embodiment shown in FIG. 1, there are four input ports 2 a, 2 b,2 c, and 2 d, and four decryption engines 20 in the digital signalprocessor 4, though in other embodiments different numbers of inputports and decryption engines may be used. The digital signal processor 4may store decryption keys used to update decryption codes of therespective decryption engines 20. The decryption keys may be stored in asuitable memory 21. In an embodiment, forty 56-bit keys may be stored ina memory 21 of the digital signal processor 4, though other quantitiesof keys with varying bit lengths may be used in other embodiments.

Clock circuit 22 may obtain a clock signal from an input port 2. Thisclock signal may be synchronized with the clock signal applied to theclock channel 9 of the input port. Phase lock loop circuit 10 may beused to maintain clock signal synchronization by recovering and cleaningclock signal irregularities. The clock circuit 22 may supply a clocksignal to digital signal processor 4. Band gap circuit 24 may supply abias current to the equalizers 16 of each input port channel 0, 1, and2.

A select signal may be sent to the control circuit 5 to select an inputport 2 that will have its audio and video data redirected to the outputport 3. A remote control unit of an audio/video device may send theselect signal to a select signal port 26 to enable the selectedaudio/video data to be sent through the output port 3. The select signalmay also be generated from any other suitable source.

The control circuit 5 may also control a digital signal processor 4. Thedigital signal processor 4 may extract video and audio data, verticaland horizontal syncs, and other control and/or status data from theserial data streams on channels 0, 1 and 2. The digital signal processor4 may then reformat the extracted data in an output format compatiblewith a digital video device. The reformatted data may be sent to thedigital video device through the output port 3.

As mentioned above, horizontal and vertical sync signal codes may beprovided on channel 0 and the relevant bit of the encryption enable codeindicating the encryption status of the next active video data frame maybe provided on channel 2. Thus, only channels 0 and 2 may be monitoredto maintain synchronization and authentication between the decryptionengine 20 of each input port 2 and the encryption engine of thecorresponding HDMI source. Since channel 1 is not needed to maintainsynchronization and authentication, the control circuit 5 may power downchannel 1 of each input port that is to be operated in a power savingmode. Channels 0 and 2 of the input ports operating in the power savingmode may stay powered up to maintain encryption authentication andsynchronization. During the powering down of channel 1, the automaticgain control channel 15 b, the equalizer circuit 16 b and the samplingcircuit 17 b of channel 1 may each be powered down as well.

The control circuit 5 may monitor channels 0 and 2 of each input port 2operating in the power saving mode for vertical sync signal codes onchannel 0, and for the relevant bit of the encryption enable codes onchannel 2 to identify encrypted frames of active video data. Each timethe control circuit 5 identifies an encrypted frame in an input port,which may be operating in the power saving mode, the digital signalprocessor 4 may update the decryption engine 20 of that input port 2 tomaintain authentication and synchronization between the decryptionengine 20 of that input port 2 and the encryption engine of thecorresponding HDMI source (not shown).

Continuous updating of input port decryption engines 20, which may beoperating in the power saving mode, ensure that the decryption engines20 may be continuously authenticated and synchronized with theencryption engines of the respective corresponding HDMI sources. Thus,when an encrypted video signal in an input port 2 operating in the powersaving mode is selected for output, virtually no delay occurs inprocessing the serial digital data streams from the newly selected inputport 2 and then outputting the corresponding audio video data signal onthe output port 3. This is because the decryption engine 20 of the newlyselected input port 2 has been continuously authenticated andsynchronized with the encryption engine of the corresponding HDMIsource, regardless of whether the input port 2 is operating in a powersaving mode or not.

To enter the power saving mode, the control circuit 5 may send adeactivate signal to each input port 2 other than a selected input port2 having a signal connected to the output port 3 for output. Thedeactivate signal may power down channel 1 of each non-selected inputport 2 to operate these ports in the power saving mode. An activatesignal may be sent by the control circuit 5 to an input port 2 to powerup channel 1 of that input port 2.

To start the authentication process, each display data channel may carrya write signal from a source connected to an input port 2. The writesignal may represent an authentication to start the process ofauthenticating the decryption engine 20 coupled to the input port 2connected to the source. The control circuit 5 may monitor the displaydata channels of the input ports for such authentication requests.

During an authentication request, an HDMI source submitting the requestmay submit a key selection vector AKSV over its display data channel 11along with other data that is stored in memory 28. Once the controlcircuit 5 allows the digital signal processor 4 to access the encryptionkeys in key memory 21, the digital signal processor 4 may read the AKSVand other data from memory 28, and then may produce a decryption codefor the engine 20 from the decryption keys retrieved from key memory 21based on the AKSV. The digital signal processor 4 may also make its ownkey selection vector BKSV available to the source to ensureauthentication of the decryption engine 20.

To decrypt data, the serial digital data streams on each channel 0, 1,and 2 of a selected input port 2 may be clocked into the digital signalprocessor 4 based on a clock signal generated by clock signal generatingcircuit 22. The clocked data may then be de-serialized and decrypted bythe corresponding decryption engine 20 using the decryption code. Thedecrypted data, including the digital audio/video signal, horizontaland/or vertical sync signals, and any other control or status data maythen be sent to the output port 3 by the digital signal processor 4 toanother digital signal processing device, such as a television, digitalvideo projection, or other device.

To avoid the situation in which multiple authentication requests arereceived simultaneously or sufficiently close in time thatauthentication of at least two engines 20 in two input ports 2 wouldoverlap, the control circuit 5 may use a queue to limit access to theencryption keys.

The control circuit 5 may be programmed to limit access to thedecryption keys in key memory 21 to the digital signal processor 4 sothat only one decryption engine 20 may be authenticated at a time. To dothis, the control circuit 5 may queue authentication requests so thatthey are processed in the order they may be received.

To detect authentication requests, the control circuit 5 may sample thedisplay data channels 11 of input ports 2 for key exchange informationat a higher sampling frequency than the frequency at which data isprovided. For example, a 100 kHz I2C protocol on the display datachannel may be sampled at a higher frequency, such as 50 MHz toarbitrate multiple authentication requests within a single 100 kHzcycle.

Referring now to FIGS. 3 and 4, a data processing system 29 may processdigital data received from each channel 0, 1, and 2 through a firstdigital data processing element 30, a second digital data processingelement 31, a third digital data processing element 32, and a fourthdigital data processing element 33. These data processing elements 30 to33 may be serially disposed in a digital data path 35. The dataprocessing system 29 may also be implemented in the digital signalprocessor 4.

Each of the first three data processing elements 30, 31, and 32 mayinclude sub-digital data processing elements 30 a-30 c, 31 a-31 c, and32 a-32 c. Sub-processing elements 30 a, 31 a, and 32 a, may processdigital data on channel 0, while sub-processing elements 30 b, 31 b, and32 b may process digital data on channel 1, and sub-processing elements30 c, 31 c, and 32 c on channel 2.

Elements 30 a, 30 b, and 30 c may receive serial data from respectivechannels 0, 1 and 2 and convert the serial data to parallel data.Elements 30 a, 30 b and 30 c may also extract control codes from theserial digital data on each respective channel. The converted paralleldata may then be clocked from elements 30 a, 30 b and 30 c, to elements31 a, 31 b and 31 c, respectively, of the second data processing element31. This clocking, however, may be delayed until all of the paralleldigital data being produced by the first elements 30 a, 30 b, and 30 cis valid as will be described below.

Elements 31 a, 31 b and 31 c may each include a delay to delay the dataat each element until valid data received from elements 30 a, 30 b and30 c have been aligned. The aligned data may then be clocked fromelements 31 a, 31 b and 31 c to respective elements 32 a, 32 b, and 32 cof the third data processing element 32. However, as described below,this clocking may not occur until the data from elements 31 a, 31 b, and31 c is valid and aligned.

Elements 32 a, 32 b, and 32 c may decode TMDS (transitional minimizeddifferential signalling) and/or TERC4 (TMDS error reduction coding)encoded signals into natural binary. The digital data may then beclocked from elements 32 a, 32 b and 32 c to a fourth data processingelement 33 to execute high bandwidth digital content protection (HDCP)on the data. However, this clocking may occur only when the data atrespective elements 32 a, 32 b, and 32 c is valid, as described below.

To ensure that only valid data is clocked into the respective first,second, third and fourth data processing elements 30, 31, 32 and 33,each of these data processing elements 30, 31, 32 and 33 andsub-elements 30 a-30 c, 31 a-31 c, and 32 a-32 c may remain disableduntil data from the immediately preceding element is determined to bevalid. Subsequent data processing elements 31 to 33 may be progressivelyenabled, for example, only when valid data is processed at the precedingelement 30 to 32. In an embodiment of the invention the second, thirdand fourth data processing elements 31, 32 and 33 may be disabled bybeing maintained in a powered down state, and may be enabled by beingpowered up.

The control circuit 5 may include a power up controller block 42, andfirst, second, third, and fourth control blocks 37, 38, 39 and 40. Thepower up controller block 42 may send a signal to power up and/or powerdown one or more data processing elements, such as elements 31, 32, or33, in a channel, such as channel 1. The first control block 37 maydetect signal alignment of all three channels (if, for example, channel1 is not disabled) and adjust delay in elements 31 a-c accordingly, bywaiting for a combined data enable signal. The combined data enablesignal may be obtained from the control codes extracted from the serialdata as it is being converted to parallel data in the sub-dataprocessing elements 30 a, 30 b and 30 c. The presence of a combined dataenable signal in the data from the three sub-data processing elements 30a, 30 b and 30 c may indicate that valid data is being produced by theseelements 30 a, 30 b, and 30 c. If one or more of the channels aredisabled or powered down, for example, channel 1, then the first controlblock 37 may detect alignment and adjust delay in the remainingchannels, such as channels 0 and 2. A power up signal from the power upcontrol block 42 may be used to begin powering up one or more of theprocess elements of the powered down channel. A power up signal from thepower up control block 42 may also be used by other control blocks, suchas first control block 37, to begin re-including the powered controlblock after detecting a combined data enable signal in the powered upchannel. Thus, in the case of the first control block 37, the firstcontrol block 37 may begin detecting alignment and adjusting delay inall three channels again after the first control block 37 detects apower up signal from the power up control block 42 to power up channel1, and the first control block 37 detects a combined data enable signalin all three channels.

After detecting the power up signal from the power up control block 42,the first control block 37 may wait until it detects a rising edge orother trigger of the data enable signal in the powered up channel beforebeginning to align the data in the powered channel with the remainingpowered up channels.

Second control block 38 may also wait until it detects a power up signalfrom the power up control block 42 indicating that respective processingelements in a powered down channel are being powered back up. Afterdetecting the power up signal from the power up control block 42, thesecond control block 38 may then wait until it detects a data enablesignal, such a corresponding rising pulse edge, on the channel beingpowered up before it begins to detect or extract a preamble signalindicating that the data in the powered up channel is valid packet dataor valid video data.

The blocks 39 and 40 may merge data enable signals on the channels. Thepower up signal from the previous block 38 may be delayed by thepipeline of the decoder elements 32 a, 32 b and/or 32 c so that the datahas sufficient time to be processed by the decoding elements 32.

FIG. 4 shows exemplary functionality of the control block 42 and first,second, third, and fourth control blocks when processing data. A powerup control block 42 of the control circuit 5 may output activationsignals to control blocks 37, 38, and 39 as well as to components and/orprocessing elements of a channel, such as channel 1 when channel 1 is tobe switched from a powered down mode to a powered up mode. The power upcontrol block 42 may also output deactivation signals as well when thechannel is to be switched from a powered up mode to a powered down mode.Upon receiving the activation signals, one or more of the controlblocks, such as first or second control blocks 37 or 38, may beginmonitoring the channel to be powered up to detect a rising edge of dataenable signal on the powered up channel.

Once the rising edge of the data enable signal is detected on thepowered up channel, the control block may begin processing the channeldata. For example, once the first control block 37 detects a rising edgeof the data enable signal on the powered up channel after receiving theactivation signal indicating that the channel was being powered up, thefirst control block 37 may begin aligning the data in the recentlypowered up channel with the other channels.

Similarly, once the second control block 38 detects a rising edge of thedata enable signal on the powered up channel after receiving theactivation signal indicating that the channel was being powered up, thesecond control block 38 may begin extracting a preamble signal from thepowered up channel identifying data as video data or packet data. Thethird and/or fourth control blocks 39 and/or 40 may not include the dataenable signal from the powered up channel in the merging of the dataenable signals until the corresponding power up from block 38 is activeand the pipeline delay of the TDMS/TERC4 decoder 32 has elapsed.

Similarly, when deactivation signals from the power up control block 42are received at one or more of the other corresponding control blocks,those control blocks may begin to ignore data in the channel to bepowered down.

When switching from one input port 2 to another input port 2 in order tochange the audio and video data being supplied to the output port 3, thecomponents of channel 1 of the newly selected input port 2 may bepowered up sequentially. The digital data processing system 29 may beoperated as previously discussed to process data received on channels 0,1 and 2 of the newly selected port 2. Sending data to each dataprocessing element only when valid data is detected at a precedingprocessing element may ensure that only valid data is produced at thefourth data processing element 33. Assuming that the decryption engine20 of the newly selected input port 2 is already authenticated andsynchronized with the encryption engine of the corresponding HDMI sourceas previously discussed, the only remaining delay in switching from oneinput port 2 to another input port 2 is the time required to activatethe components of channel 1 of the newly selected input port 2. Ingeneral, this may not require more than 3 milliseconds. Moreover, thepipelining delay in pipelining the data through the first, second, thirdand fourth digital data processing elements 30 to 33 may take no morethan a few clock cycles. Thus, the time required to switch input portsis greatly reduced.

Control circuit 5 may also be programmed to power down the components inthe channel 1 of each input port 2 that is to be operated in the powersaving mode. These components may be powered down in a predefinedsequence to minimize and/or avoid power surges that may destabilize thechannels 0, 1 and 2 of the selected input port 2 and may distort theaudio/video signal being outputted through the output port 3. Thecomponents may also be powered up in a predefined sequence for the samereasons.

When powering up an input port 2 operating in the power saving mode, theautomatic gain control, the equalizer and the sampling circuit ofchannel 1 may be powered up in sequence with the automatic gain controlcircuit 15 b of channel 1 being initially powered up, followed by theequalizer 16 b of channel 1, and then the sampling circuit 17 b ofchannel 1 being powered up. A time delay of 1 millisecond may providedbetween the powering up of each these circuits 15 b, 16 b, and 17 b.

When powering down an input port 2 to enter a power saving mode, theautomatic gain control 15 b, the equalizer circuit 16 b and the samplingcircuit 17 b of channel 1 of that input port 2 may be powered down inthe reverse sequence. Thus, sampling circuit 17 b may be powered downfirst, followed by equalizer 16 b, and then automatic gain control 15 bof channel 1. A time delay of 1 millisecond may also be provided betweenpowering down of each of these circuits 17 b, 16 b, and 15 b.

FIG. 5 shows a block representation of a different embodiment of theinvention. In this embodiment, the HDMI circuit 1 may include multipleHDMI sinks 25, namely n HDMI sinks where n may be any integer greaterthan one. In some embodiments, the number of sinks n may be in the orderof four to six. Each of the HDMI sinks 25 may be similar in design andfunction. Each of the HDMI sinks 25 may process HDMI digital audio andvideo data from respective HDMI sources connected to the input port 36of each respective sink 25 to generate processed audio and video signalsin a format recognized by a digital signal processing device connectedto a primary output 54 of the circuit 1. In some instances, the digitalsignal processing device connected to the primary output port 54 may bea television or other display device, though other devices may be usedin other embodiments.

Each of the output ports 28 of the HDMI sinks 25 may be connected to theprimary output port 54 of the circuit 1 through digital data paths. Eachof the digital paths may include a set of first data paths 12 thatconnect the output ports 28 of each sink 25 to a respective input port14 of a multiplexer 55. The digital paths may also include a second datapath 56 that connects an output port 57 of the multiplexer 55 to theprimary output 54 of the circuit 1. The multiplexer may be configured toselectively apply processed auto and video signals from an output port28 of a selected sink 25 to the primary output 54 of the circuit 1.

A selecting circuit 59 may send a sink select signal to instruct themultiplexer 55 to select a desired sink 25 output port 28 that is to beselectively applied to the primary output 54 of the circuit 1. Anexternally generated source select signal may be received at an inputterminal 60 and transmitted to the selecting circuit 59 to select thedesired sink 25 output port 28. The selecting circuit 59 may output asink select signal to the multiplexer 55 in response to receiving asource select signal from the input terminal 60. The source selectsignal may be applied to the input terminal 60 from different sources,such as a handheld remote control device or a device to which theprocessed digital audio and video signals are applied through theprimary output port 5.

FIG. 6 shows a block representation of another embodiment of theinvention. In this a HDMI circuit 50 may be similar in design to circuit1. For example, circuit 50 may include multiple sinks 25, each sink 25having an input port 36 and output port 28. Just as in circuit 1,circuit 50 may have two or more sinks 25 similar to the sinks 25 used incircuit 1.

A difference between circuit 50 in FIG. 6 and circuit 1 in FIG. 5 isthat the sink 25 output ports 8 in circuit 50 may be directly connectedto the primary output port 54 of the circuit 50 instead of beingconnected to the primary output port 54 through a multiplexer 55 as incircuit 1. In circuit 50, the first data paths 51 may connect the outputports 28 of each sink 25 to a connector 53 that connects the first datapaths 51 to second data path 52 connected to the primary output port 54.

The selecting circuit 59 in circuit 50 may also be responsive to asource select signal received at input terminal 60. However, in thisembodiment, the output ports 28 of each sink 25 may be selectivelyenabled and disabled according to enable and disable signals produced bythe selecting circuit 59. During normal operation, each of the outputports 28 may be disabled, except for a selected output port 28 of aselected sink 25 with processed audio/video data applied to the primaryoutput port 54 to be sent to a connected signal processing device, suchas a television.

The selecting circuit 59 may send an enable signal to the selectedoutput port 28 in response to receiving a source select signal to enablethe selected output port 28 from the input terminal 20. The enablesignal may enable data from the selected output port 28 to transmittedto the primary output port 54.

Even though non-selected output port 28 of non-selected sinks 25 may bedisabled, each of these ports 28 may continuously process data in theserial digital data streams received at each input port 36 from aconnected source. The digital signal processor 4 of each sink 25 maykeep each decryption engine 20 of each sink 25 authenticated andsynchronized with encryption engines of corresponding HDMI sourcesconnected to respective input ports 36 of the sinks 25. The digitalsignal processor 4 of each sink 25 may also continue processing the datareceived at each input port 36 and may continue sending the processeddata to the output port 28 of each sink 25.

For those non-selected sinks 25 operating in a power saving mode, datain powered down channels, such as the second channel, channel 1, may notbe processed while the sink is in the power saving mode. While thedigital signal processor 4 may continue processing data and sending theprocessed data to the output port 28 of each sink, data from the outputsof those sinks 25 that are disabled by the selecting circuit 59 may notbe outputted to the primary output port 54. Instead, only output from ansink 25 enabled by the selecting circuit 59 may have its output appliedto the primary output port 54.

Once a source select is received at input terminal 20 indicating that anew source is to be selected for output at the primary output port 54,the selecting circuit 59 may send a disable signal to the sink 25 withan input port 36 connected to the currently selected source. Theselecting circuit 59 may also send an enable signal to the sink 25 withan input port 36 connected to the new source to apply the output fromthe output port 28 of that sink 25 to the primary output port 54. Sinceeach of the sinks 25 continuously process data received on each channelof respective input port 6 and produce the processes data at therespective output ports 28 of each sink 25, once a disable output port28 is subsequently enabled, the processed data at the respective outputport 28 may be immediately applied to the primary output port 54. Thismay result in minimal delay since outputted data from the newly selectedsource may be immediately supplied to the primary output port 54 whenswitching sources.

While the digital data processing system may be located in and/or usedin conjunction with a HDMI sink, the system may also be used in anyother situation in which digital data is being processed, such as in,for example, devices using digital visual interfaces (DVI), to avoid theproduction of invalid data during data processing. Moreover, while thedigital data processing system has been described as comprising fourdata processing elements, other embodiments may include any number ofdata processing elements. Indeed, it is generally envisaged that morethan four data processing elements may be used in some embodiments.

Although each of the data processing elements have been described ascarrying out specific functions, the data processing elements may bemodified for other suitable or desired functions. Furthermore, theamount of delay, if any, associated with each data processing elementmay also vary.

The aforementioned system may be used in conjunction with a HDMI sinkboth in a power saving mode setting, when channel 1 of an input port ispowered up after being powered down in the power saving mode, and anon-power saving mode, when each of the three channels 0, 1 and 2 of aninput port is powered up after being operated in a fully powered downmode.

While the HDMI sink has been described as including four input ports, indifferent embodiments, the HDMI or other sink may include any number ofinput ports.

The foregoing description has been presented for purposes ofillustration and description. It is not exhaustive and does not limitembodiments of the invention to the precise forms disclosed.

1. A sink comprising: a switchably-enabled selector to select an inputport from a plurality of HDMI input ports to couple to an output port; acontrol circuit to detect encrypted data in a channel of the input portsand power down a circuit in a first channel of a non-selected input portwhile leaving powered up (i) a circuit in a second channel of thenon-selected input port carrying a vertical sync signal and (ii) acircuit in a third channel of the non-selected input port carrying anencryption enable code; and a plurality of decryption engines, eachcoupled to respective input ports to synchronize with a correspondingencryption engine of a data source after the control circuit detectsencrypted data in the channel of the respective input port.
 2. The sinkof claim 1, wherein the decryption engines synchronize with thecorresponding encryption engine of the data source after the controlcircuit detects encrypted data in the channel of the respective inputport, irrespective of whether the respective input port is selected atthe switchably-enabled selector.
 3. The sink of claim 1, wherein eachchannel includes at least one of: a gain control circuit to adjust again of an input signal; an equalizer circuit coupled to the gaincontrol circuit to adjust a frequency of the input signal; and asampling circuit coupled to the equalizer circuit to sample the inputsignal.
 4. The sink of claim 3, wherein the control circuit isconfigured to first power down the sampling circuit, then the equalizercircuit, and then the gain control circuit of a channel when beginningto operate in the power saving mode.
 5. The sink of claim 4, wherein thecontrol circuit is configured to first power up the gain controlcircuit, then the equalizer circuit, and then the sampling circuit of achannel when ceasing to operate in the power saving mode.
 6. The sink ofclaim 4, wherein the control circuit is configured to delay from about0.5 milliseconds to about 5 milliseconds between powering down circuitsof the channel.
 7. The sink of claim 6, wherein the control circuit isconfigured to delay from about 1 millisecond to about 3 millisecondsbetween powering down circuits of the channel.
 8. The sink of claim 7,wherein the control circuit is configured to delay about 1 millisecondbetween powering down circuits of the channel.
 9. The sink of claim 4,wherein the control circuit is configured to first power down thesampling circuits of input port channels selected for powering downbefore powering down any equalizer circuits of the respective channels.10. The sink of claim 4, wherein the control circuit is configured tofirst power down the equalizer circuits of input port channels selectedfor powering down before powering down any gain control circuits of therespective channels.
 11. A method comprising: detecting a selection ofan input port to be coupled to an output port from a plurality ofdigital video input ports; powering down a circuit in a first channel ofa non-selected input port while leaving powered up (i) a circuit in asecond channel of the non-selected input port carrying a vertical syncsignal and (ii) a circuit in a third channel of the non-selected inputport carrying an encryption enable code; detecting whether datatransmitted through at least one powered up channel of each digitalvideo input port is encrypted; and responsive to identifying thosedigital video input ports transmitting encrypted data, synchronizing adecryption engine of each identified video input port containingencrypted data with a corresponding encryption engine of a sourcetransmitting the encrypted data.
 12. The method of claim 11, furthercomprising: coupling a selected input port from the plurality of inputports to an output port; and powering down at least one channel ofnon-selected input ports to enter a power saving mode.
 13. The method ofclaim 12, wherein a channel carrying a vertical sync signal and achannel carrying an encryption enable code remain powered up in thepower saving mode.
 14. The method of claim 11, further comprisingproviding the decryption engines with sequential access to decryptionkeys.
 15. The method of claim 11, wherein synchronizing includesauthenticating the decryption engine with the corresponding encryptionengine.
 16. The method of claim 11, wherein the plurality of digitalvideo input ports are HDMI ports.